The invention relates to a brush seal, in particular a brush seal for reducing leakage of gas in a gas turbine engine, and a method for the manufacture of such a brush seal.
Static gas seals and seals which are required to seal around a rotating shaft are often circular in shape and are configured so that each of the bristle elements is set at an angle of approximately 45.degree. to a tangent to the circular holder. In the case of a shaft seal, the direction of inclination of the bristles corresponds to the direction of rotation of the shaft. Such seals are designed with bristles of sufficient density and length to ensure reliable sealing.
In FIG. 1 a gas-turbine clamp member containing a brush seal assembly is shown taken from a co-pending patent application GB 9510069.9 of the present applicants and which includes a pair of inner seals 72 and a pair of outer seals 71. The seals comprise a respective holder 80 and a set of bristle elements (a bristle pack) 73, 75 secured in the holder. Each bristle pack consists of a secured end embedded or clamped in its holder and a free or exposed end designed to abut against a surface to be sealed.
The inner bristle packs 73 are, in use, urged against respective adjacent inner annular duct sections interfacing a combustion chamber with the turbine blade housing, while the outer bristle packs 75 are likewise urged against respective adjacent outer sections. The pairs of inner and outer seals at the two ends of the seal assembly serve to seal off the space between, respectively, the incoming inner and outer duct sections and the outgoing inner and outer duct sections. Thus, in use, it is intended that there be a gas-tight seal between incoming outer duct, one of the outer bristle packs 75, neighboring inner bristle pack 73 and the incoming inner duct on the one hand, and between the outgoing outer duct, the other of the outer bristle packs 75, the neighboring inner bristle pack 73 and the outgoing inner duct on the other. Thus, the action of the seals is to close off the space between the inner and outer ducts at each end.